import java.util.Scanner;

public class Sizhang {
	public static void main(String[] args) {
	Scanner in = new Scanner(System.in);
	/*System.out.println("请输入班级人数");
	int num=in.nextInt();
	double score=0;
	int i=1;
	double sum=0;
	boolean isWrong=false;
	while (i<=num) {
		System.out.println("请输入第"+i+"个学院成绩");
		score=in.nextDouble();
		if (score<0) {
			isWrong=true;
			break;
		}
		sum +=score;
		i++;
	}
	if (isWrong) {
		System.out.println("录入错误");
	}else {
		double avg=sum/num;
		System.out.println("平均成绩"+avg);
	}*/
	System.out.println("请输入班级人数 ");
	int num=in.nextInt();
	int score=0;
	double dayu=0;
	int i=1;
	while (i<=num) {
		System.out.println("第"+i+"个学员成绩");
		score=in.nextInt();
		i++;
		if (score<80) {
			continue;
		}
		dayu++;
	}
	double a=dayu/num;
	System.out.println(a);
	}
}
